Gravity electrostatic separation process



May 10, 1938. R. H. BEDFORD GRAVITY ELECTROSTATIC SEPARATION PROCESS Filed March 24, 1956 g. A449 AZ-WWL IN VEN TOR.

kmmu Patented May 10, 1938 PATENT OFFHIE GRAVITY ELECTROSTATIC SEPARATION PROCESS Robert Hardy Bedi'ord, Los Gatos, Calif.

Application March 24, 1936, Serial No. 70,638

2 Claims.

My invention relates to' electrostatic separation processes, and particularly relates to a separating process in which the force of electrostatic attraction is made to act in the same direction as, reinforces, andis added to, the force of gravity.

The force of electrostatic attraction is applied;

Firstly, by charging the material to be separated, such as a mixture of particles of ore, by contact .with an electrode which is connected to one pole of a source of static electricity.

Secondly, by agitating this charged material upon a dielectric beneath which is the other electrode, which is connected to the other and oppositely charged pole of the source of static electricity.

When the mixture to be separated is brought into contact with the charged electrode each of its component particles is charged electrically to a degree that varies with its composition.

In general the conducting particles are charged and the non conducting particles are uncharged,

or not charged.

The charged conducting particles of the mixture to be separated thus constitute one electrode of an electric condenser, toward the opposite electrode of which they are attracted. The uncharged, non conducting particles are not so attracted.

The direction of this force of electrostatic attraction can be controlled by the relative positions of the charged particles, which form one electrode, and the other and oppositely charged electrode; and the direction of this force of electrostatic attraction is made to coincide with the direction of the force of gravity by placing the latter electrode beneath the former electrode.

When the mixture of charged and uncharged particles is agitated under these conditions the charged particles rapidly find their way to .the bottom of the bed of moving material, under the joint forces of electric attraction and gravity, the eflfect being that of increasing the specific gravity of each charged particle by the amount of this force of electrostatic attraction.

Agitation is effected by a current of air.

The accompanying drawing shows, in vertical section, in a diagrammatic way an illustrative embodiment of apparatus for carrying out the process; using a current of air for agitation.

As indicated in the illustrative drawing showing diagrammatically apparatus for carrying out the process, the material to be separated is fed by the hopper I, which is connected by the wire 2', to the positive pole of the source of static electricity. This charged material falls upon the permeable dielectric 3, where it is agitated;

by an adjustable current of air supplied through tailing discharge, l I.

pipe 4; above the wire screen 5, which is connected by wire 6, with the negative pole of the source of static electricity.

The charged particles, 1, and the charged screen 5, thus constitute the electrodes of a condenser, separated by the dielectric 3. These charged particles, 1, are attracted toward the underlying electrode, 5. by this force of electrostatic attraction, which thus acts in conjunction with, reinforces, and is added to, the force of gravity.

The charged particles, I, which are concen trates, escape via the adjustable gate, 8, over the concentrate discharge, 9; the noncharged particles, III, which are tailings, escape over the This arrangement permits continuous operation and automatic discharge of the diiierent products.

The walls, l2, of the separator, which may be made of any strong material, are bolted to the lower portion, l3, of the apparatus. When, as shown here, the part I3 is of metal, it must be insulated .by the dielectric gasket, H, from the electrode, 5. When bolted together these parts form in effect a box which is airtight except for the permeable dielectric 3.

The hood, I5, is connected to a suction apparatus which removes dust.

Having described this process in connection with an illustrative mode of carrying the same into effect, to the details ,of which I do not desire to be limited, what I claim as new and what I desire to secure by Letters Patent is set forth in the appended claims.

1. The process of separating conducting and non-conducting particles of different specific gravities consisting in subjecting the mixed particles to an electrostatic charge of one sign and then depositing the particles upon a nonconducting permeable support having therebelow an electrode charged to a potential of opposite sign, agitating the particles by means of a gaseous current passed upwardly through. the permeable support, thereby settling the conducting particles to a lower stratum, and separately discharging the stratified components.

2. The process of separating particles of materials of diiferent electrical conductivities consisting in subjecting the mixed particles to an electrostatic charge of one polarity and then depositing the particles upon a nonconducting permeable support having therebelow an electrode charged to an opposite polarity, agitating the particles by means of a gaseous current passed upwardly through the permeable support, thereby causing a stratification of the particles, and separately discharging the stratifled components.

ROBERT HARDY BEDFORD. 

